The invention is described below using the example of motor vehicle bodies as objects, but the invention relates also to devices for other objects whose temperature must be controlled in a production process. When the term “temperature control” is used here, it means the inducement of a specific temperature of the object that the object does not initially possess. It can be a temperature increase or a temperature reduction. “Temperature-controlled air” is understood as meaning air that has the required temperature for controlling the temperature of the object.
A frequent case of the temperature control, namely the heating, of motor vehicle bodies in the automotive industry is the operation of drying wet motor vehicle bodies or of drying the coating of a motor vehicle body, whether that be a paint or an adhesive or the like. Wet objects other than motor vehicle bodies or the coating of other objects can correspondingly be dried. The detailed description of the invention which is given below is made using the example of such a drier for motor vehicle bodies.
When the term “drying” is used here, it means any operations in which the coating of the motor vehicle body, in particular a paint, can be made to cure, whether that be by the expulsion of solvents or by the crosslinking of the coating substance.
Devices of the type mentioned at the beginning that are known on the market are used for drying freshly painted motor vehicle bodies and are heated, inter alia, by extracting air from tunnel portions that are short compared with the overall length of the drying tunnel, heating it in a heater assembly by means of a heat exchanger, and feeding it to the corresponding tunnel portion again in a circuit.
In the drying of freshly painted motor vehicle bodies, the air removed from the tunnel portion is loaded mainly with solvent, which is released in the drying operation. This air additionally contains coating constituents which are released during the drying of the motor vehicle body; nevertheless, for the sake of simplicity, reference will be made only to waste air below.
In known devices, the burner air necessary for operating the burner unit is removed from the surroundings via a separate air compressor fan. Accordingly, the burner air must be heated from ambient temperature to the burner temperature and is removed from the surroundings as clean air, which is contaminated during use and can optionally be purified before being returned to the surroundings.